General Principles for FDG PET Dementia Imaging

The use of PET radiotracers allows molecular imaging of brain processes. In clinical practice, there are two such tracers in use for dementia: F-18 FDG and F-18 Amyloid binders.

In general, FDG PET is highly sensitive in distinguishing Alzheimer's dementia (AD) from other neurodegenerative disorders which look clinically similar. This is a pattern associated with Alzheimer's dementia: decreased metabolism in the temporoparietal cortex and posterior cingulate gyrus with sparing of the primary sensorimotor cortex, occipital cortex and subcortical structures. The decrease may be asymmetric, and in more advanced cases tend to be symmetric in these area and also decreased in the frontal cortex

On the other hand, "Amyloid PET" is promoted as more specific for AD, although the FDA dictates the interpretation be on amyloid plaque burden in the cortex.

Below are normal FDG patterns on PET imaging, including of normal aging changes (primarily brain atrophy, which decreases FDG activity in parts of the brain that is more robust in younger healthy people).

On FDG PET/CT, in general and in early stages:

Alzheimer dementia is associated with decreased temporoparietal and posterior cingulate activity with sparing of the pre-/postcentral gyrus and occipital cortex

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